AS Level Computer Science WJEC.- Hardware - Processor

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What is a Von Neumann Processor made up of?
A Control Unit, an Arithmetic Logic Unit, and Registers
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What other units are used in the Von Neumann architecture? (Not strictly within the CPU)
Buses and Memory.
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Describe the purpose of the Control Unit
The Control Unit manages the execution of machine code by sending control signals to the rest of the computer, such as Memory, Input Devices, and Output Devices, along a Control Bus. It also manages the Fetch Decode Execute cycle.
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What else does the Control Unit achieve by use of its Internal Clock?
Part of the control unit's role is to synchronise instructions using its internal clock. How many times this is done per second is known as the clock speed, and a 'tick' of this clock is known as a Clock Cycle.
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Describe the purpose of the Arithmetic Logic Unit
This Unit is responsible for calculations and logical operations. Calculations can include multiplication of floating points, or division of integers, while logic operations include greater than and other comparisons. This allows programs to decide.
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Describe Registers
Registers are small blocks of memory, typically used as temporary storage for instructions as they are processed. Registers run at the same speed as the processor, and there are several types of them. Machine code only works when loaded in a register
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What is the (PC) register?
The Program Counter register stores the address in of the next instruction to be fetched.
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What is the (MAR)?
The Memory Address Register holds onto the address of an instruction or piece data to be fetched. Once complete, the address stored in the PC is copied onto the MAR, and the PC accumulates.
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What is the (MDR)?
Once the MAR fetches an instruction or piece of data, it is loaded onto the MDR for storage.
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What is the (CIR)?
The Current Instruction Register holds onto the current instruction so that it can be executed. Once the instruction is complete, it copies any instruction on the MDR onto itself.
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What is the (ACC) register?
The Accumulator is where results of calculations are stored, and as calculations are a step by step process in processors, the value of the Accumulator is what is used to calculate at the next step.
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What is the point of the MDR existing when the CIR can hold onto the same information?
To carry out a process known as pipelining. This is where, because instructions can take a long time to retrieve, we get that instruction before the current one is finished being executed, and storing it in the MDR.
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What is Parallel Processing?
This is when we use multiple processors to process several things at once. This means that we can decrease the time taken to process tasks dramatically by breaking them down into threads. However, programs must be written with this in mind to use it.
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Summarize the Fetch, Decode, Execute cycle.
The FDE cycle is what we use to carry out tasks. First we retrieve our instruction, then we figure out what the instruction is demanding, and then we carry out that instruction. We repeat this many times per second.
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Describe how the Fetch portion of the FDE cycle is carried out.
To find the next instruction after finishing the last one, we simply copy the PC onto the MAR, the PC then increments to the next address in line, and the MAR then retrieves the next instruction, loading it onto the MDR.
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Explain how we can perform 'jumps' in machine code, thanks to how we perform Fetching.
By manipulating the PC before requesting the next instruction, we can choose what address the PC contains, and therefore, what it copies onto the MAR. This means instructions for 'jumps' simply shift the address of the PC to new points in memory.
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Describe how the Decode and Execute portion of the FDE cycle is carried out.
The next instruction in line, stored within MDR, is copied over to CIR, where the opcode is identified, and hence, decoded. Depending on the opcode identified, different actions are taken to execute the instruction.
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What is the equation for frequency, and hence, the equation for time using frequency?
frequency = 1 / time, hence, time = 1 / frequency.
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What are the three BUS types, and what is their purpose?
Address Bus - Carries an identification about where data is being sent. Data Bus - Carries the actual data. Control Bus - Car
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Other cards in this set

Card 2

Front

What other units are used in the Von Neumann architecture? (Not strictly within the CPU)

Back

Buses and Memory.

Card 3

Front

Describe the purpose of the Control Unit

Back

Preview of the front of card 3

Card 4

Front

What else does the Control Unit achieve by use of its Internal Clock?

Back

Preview of the front of card 4

Card 5

Front

Describe the purpose of the Arithmetic Logic Unit

Back

Preview of the front of card 5
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